Mechanism for feeding pulverized coal.



W. R'. DUNN. MEGHANISM FOR PEBDING PULVERIZED GOAL.

APPLICATION FILED APR. 9. 1909.

Patented Apr. 12,1910.

2 SHEETS-SHEET 1.

W. R. DUNN.

MEGHANISM POR FEEDING PULYERIZED GOAL.

APPLICATION FILED APR. 9. 1909.

954,944. Patented Apr. 12, 1910. n

2 SHEETS-SHEET 2.

WI NESSES:

UNITED sTATEs PATENT oEEIoE.

MECHANISIVI FOR FEEDING PULVERIZED COAL.

Specification of Letters Patent.

Application filed April 9,

Patented Apr. 12, 1910.

1909. serial No. 488,889.

' which an air blast is employed to blow the coal into the combustion chamber.

The object of the invention is to provide feeding mechanism of the kind which will be relatively simple in construction and reliable in operation and which will insure a uniform and continuous feed of the powdered coal into the air blast chamber.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, however, reference may be had to the accompanying drawings and descriptive matter, 1n which I have illustrated and described one of the forms in which the invention may be embodied.

Of the drawings: Figure 1 isa somewhat diagrammatic elevation of the feeding mechanism. Fig. 2 is an enlarged sectional view of a portion of a feeding mechanism embodying my invention. Fig. 3 is a sectional.

plan of a portion of the conveyer chamber showing the discharge orifices. Fig. 4C is an elevation partly broken away and in section showing a modified construction. Fig. 5 is a sectional elevation taken on the line 5-5 of Fig. 4. Fig. 6 is a view similar to Fig. 3, but showing a modified arrangement of the discharge orifices, and Fig. q? is a plan view of an air regulating valve which may be used.

Referring rst .to the construction shown in Figs. 1, 2 and 3, A represents-a hopper filled with powdered coal and provided at its lower end with the section A1 of a screw conveyer casing which is connected by the tubular casing section B to the chute' D, through which the coal is assed into the air blast chamber E, from W ich it is blown by air under pressure supplied by the noz- 1 zle E1 through the tube E2 into the combustion chamber of furnace F.

The powdered coal is fed with the proper speed through the casing sections A1 and B into the chute D. by means of a screw C, formed with one or more spiral ribs C1. The screw C has secured to it at one end a beveled gear C3, whichis driven at the proper speed by a beveled driving gear C4. The chute is divided into upper and lower chambers D1 and D2 by means of a curved wall D3. The wall of the chamber D1 is shaped and arranged to closely surround the' screw C and forms in effect a third section of the inclosing casing of the screw conveyer. The chamber D2 opens at its lower end into the blast chamber E through the connecting nipple D6.

Discharge orifices are formed in the wall D3, which are distributed along a considerable portion of the wall D3 in a direction parallel to the length of the screw conveyer C and are restricted circumferentially, so that the powdered coal cannot be discharged entirely through a short section of the casing length, but must take place along a considerable extent of the casing length. By this arrangement of restricted ports, I insure that the powdered coal is .discharged in fine streams into the chamber D2 and prevent the coal from being discharged from the masses. The coal thus fed in comparatively thin streams into the chamber D2, passes with a very desirable uniformity into the air blast chamber. On account of the more or less flocculent nature of the powderedcoal, the coal particles tend to separate from one another as they pass through the chamber D2. The flocculent coal particles are to some extent held in suspension, or rather retarded, during their passage through the chamber D2, by the air in the chamber, and Isometimes find it desirable to provide means for obtaining a regulated leakage of air into the chamber D2 in order to regulate the air pressure therein and to obtain the desired feed of the coal under varying conditions.

In the form of the apparatus shown in the drawings a threaded aperture D8 is formed in the upper side of the wall of the compartment D1 adjacent the port D7 and in this aperture is screwed the body portion H of a valve mechanism which I may employ for regulating the admission of air into the screw conveyer intermittently in chunks orl chamber D1 and thereby into the chamber e i D2 of the chute D. The member I-I is provided with a/ series of ports Ill and supports a screw H2 forming a journal for a disk H3 provided with apertures or ports Ht which may be moved into more or less complete register with the ports H1. A handle H5 is shown for adjusting the disk H3.

The valve mechanism described forms a simple and effective means for regulating the leakage of air into the upper portion of the chamber D2. It will of course be understood that the operation of the air jet from the nozzle El is to partially exhaust the air from the chamber D2 and I nd it desirable usually to supply appreeiably more air to the chamber D2 than passes into that chamber with the powdered coal. The adjustable valve mechanism disclosed forms a simple and convenient means for obtaining and regulating the quantity of this leakage. If the valve mechanism H described is not provided, or is found not to admit a sufcient quantity of air at any time, the air may be admitted through the port- D5l in the side wall of the chamber D2 which may be more or less completely closed by the cover D5. The cover D5 may be removed when desired to permit the discharge of the coal into the compartment D2 to be observed. Vith the arrangement described I avoid the trouble which I have found by extended experience occurs from time to time when screw conveyers are employed which discharge from one or more relatively large orifices directly into an air blast. In such cases disturbances in the operation of the apparatus are produced by the passage into'the air blast of the powdered coal in chunks or masses of particles which adhere together, thus preventing the uniform feed of the fuel into the combustion chamber which is necessary for proper operation. Nith the restricted and distributed port arrangement described and the provision of a chamber between the discharge ports and the air blast chamber in which the more or less Hocculent coal particles may lose their adherency, so to speak, for one another, I obtain a more satisfactory and uniform feed for the powdered coal than has heretofore been possible l The exact shape and arrangement of the discharge orifices is obviously immaterial in obtaining the desired results. Examples of different arrangements are shown in Figs. 3 and 6. In the form shown in Fig. 3, a row of circular perforations D4 are formed in the wall D3 and a large perforation D7 is formed in the wall D3 at the inner end of the row of perforations D4', the perforation D7, it will be understood, takes care of any material which is not discharged through the ports D4. Instead of the circular ports D, I employ in the construction shown in Fig. 6 one or more relatively narrow slots DB which are elongated inthe direction of the length of the screwn In the form shown in the drawings, the screw C is provided with two ribs (il, and it will be understood that the provision of a plurality of ribs C1 on the screw conveyer C assists in obtaining the desired uniformity of feed.

In order to more accurately regulate the fuel discharge through the lateral ports of the conveyer casing, it may, in some cases, be desirable to provide means for adjusting the etl'ective discharge area of the ports in order to better control the feed. This is parti@ ularly advantageous when the coal is apt to vary in character from time to time. 011e arrangement which I may use for adjusting the discharge orifices is shown in Figs. Ll and 5, where I provide a slide Gr having oriiices (ll which may be moved into more or less complete register with the orifices D by moving the slide bodily in a direction transverse to the chamber D1. The slide G may be conveniently adjusted by means of the hand wheel I and screw I to which the hand wheel is threaded. The screw I is threaded into a tapped lug D formed in the chute l) and is swivelcd in a lug G2 depending from the portion G3 of the slide G extending through the side of the chute.

Having now (,lescribed my invention.r what I claim as new, and desire to secure by Letters Patent, is: i

l. In mechanism for blowing powdered coal into a combustion chaml'a'ir, the combi nation with an air blast chamber of a second chamber located above and opening at its lower end into said air blast chamber, and means for feeding powdered coal .into said second chamber above its lower end, comprisinga rotary screw and an inclosing casing therefor se perforated as to provide a lateral. port area distributed longitudinally and restricted circumfercntially ofthe screw,

` so that the discharge will take place along a considerable extent of the length of the screw.

2. In mechanism for blowing powdered coal into a combustion chamber, the combination with an air blast chamber of a sec,- ond chamber located above and opening at its lower end into said air blast chamber, means for feeding powdered coal into said second chamber above its lower end, comprising a rotary screw and an inclosing casing therefor so perforated as to provide a lateral port area distributed longitudinally and restricted circumferentially of the screw, so that the discharge will take place along a considerable extent of the length of the screw, and means for regulating the air pressure in said second chamber.

3. In mechanism for blowing powdered coal into a combustion chamber, the combination with an air blast chamber of a second chamber located above and opening at its lower end into said air blast chamber,

means for feeding powdered coal into said second chamber above its lower end, comprising a rotary screw and an inclosing casing therefor so perforatedy as to provide a lateral port area distributed longitudinally and restricted circumferentially of the screw, so that the discharge will take place lalong a considerable extent of the length of they screw, and an adjustable valve regulating he admission of air into said second chain- 4. In mechanism for blowing powdered coal into a combustion chamber, the combination with an air blast chamber of a second chamber located above and opening'at its lower end into said air blast chamber, and means for feeding powdered coal into said second chamber above its lower end, comprising a rotary screw, an inclosing casing therefor so perforated as to provide a lateral discharge port area distributed longitudinally and restricted circumferent-ially of the screw, so that the discharge will take place along a considerable extent of the length of the screw, and means for adjusting the effective discharge capacity of said ports.

5. In mechanism for blowing powdered coal into a combustion chamber, the combination with an air blast chamber of a second chamber located above and opening at its lower end into said air blast chamber, and means for feeding powdered coal into said second chamber above its lower end, comprising amultiple threaded rotary screw and an inclosing casing therefor so perforated as to provide a lateral discharge port area distributed longitudinally and restricted circumferentially of the screw, so that the discharge will take place along a considerable extent of the length of the screw.

6. In mechanism for blowing powdered coal into a combustion chamber, the combination with an air blast chamber of aseoond chamber located above and opening at its lower end into said air blast chamber, and means for feeding powdered coal into said second chamber, consisting of a horizontal rotary screw and an inclosing casing therefor extending above the air blast chamber, said casin being formed with a plurality of restricted ports in its underside through which the coal passes into said second chamber, said ports being distributed along a considerable extent ofthe length of thel screw.

7. In mechanism for blowing powdered coal into a combustion chamber, the combination with an air blast chamber of a sec-- ond chamber located above and opening at its lower end into said air blast chamber, and means for feeding powdered coal into said second chamber above its lower end, comprising a rotary screw and an inclosing casing therefor formed with discharge ports extending along a considerable extent of the length of the casing, and a valve movable transversely to the length of the casing for adjusting the effective discharge area of said ports.

WILLIAM R. DUNN. Witnesses: v

HOWARD ZEARFASS, CEAS. B. BRUNNER. 

